1<?php
  2/**
  3 * HTTP API: WP_Http_Encoding class
  4 *
  5 * @package WordPress
  6 * @subpackage HTTP
  7 * @since 4.4.0
  8 */
  9
 10/**
 11 * Core class used to implement deflate and gzip transfer encoding support for HTTP requests.
 12 *
 13 * Includes RFC 1950, RFC 1951, and RFC 1952.
 14 *
 15 * @since 2.8.0
 16 */
 17#[AllowDynamicProperties]
 18class WP_Http_Encoding {
 19
 20	/**
 21	 * Compress raw string using the deflate format.
 22	 *
 23	 * Supports the RFC 1951 standard.
 24	 *
 25	 * @since 2.8.0
 26	 *
 27	 * @param string $raw      String to compress.
 28	 * @param int    $level    Optional. Compression level, 9 is highest. Default 9.
 29	 * @param string $supports Optional, not used. When implemented it will choose
 30	 *                         the right compression based on what the server supports.
 31	 * @return string|false Compressed string on success, false on failure.
 32	 */
 33	public static function compress( $raw, $level = 9, $supports = null ) {
 34		return gzdeflate( $raw, $level );
 35	}
 36
 37	/**
 38	 * Decompression of deflated string.
 39	 *
 40	 * Will attempt to decompress using the RFC 1950 standard, and if that fails
 41	 * then the RFC 1951 standard deflate will be attempted. Finally, the RFC
 42	 * 1952 standard gzip decode will be attempted. If all fail, then the
 43	 * original compressed string will be returned.
 44	 *
 45	 * @since 2.8.0
 46	 *
 47	 * @param string $compressed String to decompress.
 48	 * @param int    $length     The optional length of the compressed data.
 49	 * @return string|false Decompressed string on success, false on failure.
 50	 */
 51	public static function decompress( $compressed, $length = null ) {
 52
 53		if ( empty( $compressed ) ) {
 54			return $compressed;
 55		}
 56
 57		$decompressed = @gzinflate( $compressed );
 58		if ( false !== $decompressed ) {
 59			return $decompressed;
 60		}
 61
 62		$decompressed = self::compatible_gzinflate( $compressed );
 63		if ( false !== $decompressed ) {
 64			return $decompressed;
 65		}
 66
 67		$decompressed = @gzuncompress( $compressed );
 68		if ( false !== $decompressed ) {
 69			return $decompressed;
 70		}
 71
 72		if ( function_exists( 'gzdecode' ) ) {
 73			$decompressed = @gzdecode( $compressed );
 74
 75			if ( false !== $decompressed ) {
 76				return $decompressed;
 77			}
 78		}
 79
 80		return $compressed;
 81	}
 82
 83	/**
 84	 * Decompression of deflated string while staying compatible with the majority of servers.
 85	 *
 86	 * Certain Servers will return deflated data with headers which PHP's gzinflate()
 87	 * function cannot handle out of the box. The following function has been created from
 88	 * various snippets on the gzinflate() PHP documentation.
 89	 *
 90	 * Warning: Magic numbers within. Due to the potential different formats that the compressed
 91	 * data may be returned in, some "magic offsets" are needed to ensure proper decompression
 92	 * takes place. For a simple pragmatic way to determine the magic offset in use, see:
 93	 * https://core.trac.wordpress.org/ticket/18273
 94	 *
 95	 * @since 2.8.1
 96	 *
 97	 * @link https://core.trac.wordpress.org/ticket/18273
 98	 * @link https://www.php.net/manual/en/function.gzinflate.php#70875
 99	 * @link https://www.php.net/manual/en/function.gzinflate.php#77336
100	 *
101	 * @param string $gz_data String to decompress.
102	 * @return string|false Decompressed string on success, false on failure.
103	 */
104	public static function compatible_gzinflate( $gz_data ) {
105
106		// Compressed data might contain a full header, if so strip it for gzinflate().
107		if ( str_starts_with( $gz_data, "\x1f\x8b\x08" ) ) {
108			$i   = 10;
109			$flg = ord( substr( $gz_data, 3, 1 ) );
110			if ( $flg > 0 ) {
111				if ( $flg & 4 ) {
112					list($xlen) = unpack( 'v', substr( $gz_data, $i, 2 ) );
113					$i          = $i + 2 + $xlen;
114				}
115				if ( $flg & 8 ) {
116					$i = strpos( $gz_data, "\0", $i ) + 1;
117				}
118				if ( $flg & 16 ) {
119					$i = strpos( $gz_data, "\0", $i ) + 1;
120				}
121				if ( $flg & 2 ) {
122					$i = $i + 2;
123				}
124			}
125			$decompressed = @gzinflate( substr( $gz_data, $i, -8 ) );
126			if ( false !== $decompressed ) {
127				return $decompressed;
128			}
129		}
130
131		// Compressed data from java.util.zip.Deflater amongst others.
132		$decompressed = @gzinflate( substr( $gz_data, 2 ) );
133		if ( false !== $decompressed ) {
134			return $decompressed;
135		}
136
137		return false;
138	}
139
140	/**
141	 * What encoding types to accept and their priority values.
142	 *
143	 * @since 2.8.0
144	 *
145	 * @param string $url
146	 * @param array  $args
147	 * @return string Types of encoding to accept.
148	 */
149	public static function accept_encoding( $url, $args ) {
150		$type                = array();
151		$compression_enabled = self::is_available();
152
153		if ( ! $args['decompress'] ) { // Decompression specifically disabled.
154			$compression_enabled = false;
155		} elseif ( $args['stream'] ) { // Disable when streaming to file.
156			$compression_enabled = false;
157		} elseif ( isset( $args['limit_response_size'] ) ) { // If only partial content is being requested, we won't be able to decompress it.
158			$compression_enabled = false;
159		}
160
161		if ( $compression_enabled ) {
162			if ( function_exists( 'gzinflate' ) ) {
163				$type[] = 'deflate;q=1.0';
164			}
165
166			if ( function_exists( 'gzuncompress' ) ) {
167				$type[] = 'compress;q=0.5';
168			}
169
170			if ( function_exists( 'gzdecode' ) ) {
171				$type[] = 'gzip;q=0.5';
172			}
173		}
174
175		/**
176		 * Filters the allowed encoding types.
177		 *
178		 * @since 3.6.0
179		 *
180		 * @param string[] $type Array of what encoding types to accept and their priority values.
181		 * @param string   $url  URL of the HTTP request.
182		 * @param array    $args HTTP request arguments.
183		 */
184		$type = apply_filters( 'wp_http_accept_encoding', $type, $url, $args );
185
186		return implode( ', ', $type );
187	}
188
189	/**
190	 * What encoding the content used when it was compressed to send in the headers.
191	 *
192	 * @since 2.8.0
193	 *
194	 * @return string Content-Encoding string to send in the header.
195	 */
196	public static function content_encoding() {
197		return 'deflate';
198	}
199
200	/**
201	 * Whether the content be decoded based on the headers.
202	 *
203	 * @since 2.8.0
204	 *
205	 * @param array|string $headers All of the available headers.
206	 * @return bool
207	 */
208	public static function should_decode( $headers ) {
209		if ( is_array( $headers ) ) {
210			if ( array_key_exists( 'content-encoding', $headers ) && ! empty( $headers['content-encoding'] ) ) {
211				return true;
212			}
213		} elseif ( is_string( $headers ) ) {
214			return ( stripos( $headers, 'content-encoding:' ) !== false );
215		}
216
217		return false;
218	}
219
220	/**
221	 * Whether decompression and compression are supported by the PHP version.
222	 *
223	 * Each function is tested instead of checking for the zlib extension, to
224	 * ensure that the functions all exist in the PHP version and aren't
225	 * disabled.
226	 *
227	 * @since 2.8.0
228	 *
229	 * @return bool
230	 */
231	public static function is_available() {
232		return ( function_exists( 'gzuncompress' ) || function_exists( 'gzdeflate' ) || function_exists( 'gzinflate' ) );
233	}
234}
235